Hi Ben.
for powering your scope out in the field, especially if you are using a laptop then you would want at least a 35 Ah for a couple of nights if you aren't able to recharge. If at home do away with the batteries and get a regulated 12v 2 - 5 Amp transformer to run you scope.
You can try an off axis guider. some people swear by them, others hate them with a passion. I fall into the second catagory
. Withouth the OAG though you'll either need to go the guidescope route (which means guiderings, counterbalance weights for the bottom of the scope, guide camera, laptop) or a selfguiding camera (ie astrocamera SBIG FLI, Apogee, SX etc)
If you want to do terrestrial viewing, get a scope for that. The FL of the 8" is really too long for much except extreme distance viewing. A nice 60-80mm spotting scope (or normal refractor that can be used for autoguiding) would be nice.
btw starting out imaging through an 8"SCT even with a 6.3 reducer (yes you will need a T ring and T Adapter to go with the FR) will be extremely challenging. Good luck